Vero cell cultures were used for the isolation of rickettsial organisms and these agents were identified by microimmunofluorescence test. Nineteen strains of rickettsia were isolated from ixodid ticks in Vero cells. These isolates included 3 of Rickettsia sp., possibly R. rhipicephali from Dermacentor ticks in Oregon, and 13 from Massachusetts ticks; the latter isolates reacted most strongly with specific immune sera from the spotted fever-group agent, R. montana. Thirty-six strains of virus were isolated from argasid ticks. Among these strains were 6 Hughes group viruses (probably Soldado) from South Africa and 22 of another Hughes group agent (Raza) from Mexico. Utilizing immunofluorescence microscopy, we studied 52 arboviruses of 11 serogroups. BIBLIOGRAPHIC REFERENCES: Yunker, C.E., Clifford, C.M., Thomas, L.A., Keirans, J.E., Casals, J., George, J.E., and Parker, J.C.: Sunday Canyon virus, a new ungrouped agent from the tick Argas (A.) cooleyi in Texas, Acta Virol. 21: 36-44, 1977. Yunker, C.E. Thomas, L.A., and Cory, J.: Phenetic relationships of viruses of the Hughes serological group. Proc. 2nd Int. symp. on Arctic Arboviruses, Mont Gabriel, Que., Canada, May 26-28, 1977.